Electrical cable connector having an improved cable grip



Feb. 18, 1964 J. F. HEALY 3,121,600

ELECTRICAL CABLE CONNECTOR HAVING AN IMPROVED CABLE GRIP Filed Nov. 5. 1960 66 \i mmv 6 INVENTOR United States Patent 3,121,600 ELECTRICAL CABLE CONNECTOR HAVING AN IMPRGVED CABLE GREP Joseph F. Healy, Westport, Conn., assignor to Harvey Hubhell, incorporated, Bridgeport, Conn, a corporation of Connecticut Filed Nov. 3, 1960, Ser. No. 67,111 Claims. (Cl. 339-103) This invention relates to electrical wiring devices, particularly to electrical cord connectors, and more particularly to connectors for heavy duty, multiwire, electrical cable.

It is desirable in electrical cable connectors to connect the electrical cable to the connector component in such a manner that any external pull or strain on the cable is not transmitted to the usual connections within the connector component between the usual ends of the cable wires and the usual terminals that form a part of the connector component. These devices are generally known as cord clamps, particularly when associated with electrical cords of ordinary capacity, -i.e. 110-220 volts and 30 amperes, and frequently take the form of a pair of metallic clamping members that are mounted on the connector component, and so constructed and arranged as to be capable of being selectively clamped about an electrical cord in the manner of a vise. It is particularly difiioult, however, to utilize such known cord clamps to provide an eifective strain-relieving, cord clamp for heavy duty, high-capacity, multi-wire, electrical cables. These cables are capable of handling heavy electrical loads, for example, in excess of 400 volts and 50 amperes, and are usually of large diameters; it has been found in practice that known cord clamps are not suitable for these cables.

-It is an object of the invention to provide an improved cable grip for a cable connector component and particularly one which is capable of providing an effective, strainrelieving grip for heavy duty, electrical cable.

It is a further object of the invention to provide a cable grip as set forth in the preceding paragraph which is extremely simple in construction, easy to assemble, easy to operate, and functionally superior to known cord grips.

The objects of my invention are achieved in one form by providing a cable grip for a cable connector component comprising at least one deformable, resilient, tubular clamping bushing, and structurally associating it with the remainder of the connector component so as to render it deformable in a controlled manner so as to utilize it as a grip for a cable.

The above, other objects and further details of that which I believe to be novel and my invention will be clear from the following description and claims taken with the accompanying drawings wherein:

PEG. 1 is a side elevational view of a portion of an electrical cable that is to be connected to a connector component;

FIG. 2 is a sectional view taken substantially on line 22 of FIG. 1;

FIG. 3 is a side elevational view of a connector component with portions shown in section, taken substantially on line 33 of FIG. 5;

FIG. 4 is a perspective view of a clamping bushing;

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FIG. 5 is a sectional View taken substantially on line ss of FIG. 3;

FIG. 6 is a view similar to FIG. 3 but showing the" electrical cable connected to the connector component;

FIG. 7 is a sectional view taken substantially on line 7-7 of PEG. 6, and

FIG. 8 is a sectional view taken substantially on line 88 of FIG. 5.

In the drawings I have illustrated my improved cable grip as incorporated in a connector component which may, for example, be the connector body or cap of an electrical cable connector. It should be realized, however, that its applications are not limited thereto and that it may be employed with any other electrical wiring devices which have an electrical cable or cord connected to them in substantially the same manner.

FIGS. 1 and 2 illustrate a representative, multi-Wire, electrical cable 10 that is to be connected to a connector component 12, which is illustrated by itself in FIG. 3. Electrical cable 19 is dimensioned and constructed so as to be capable of performing heavy electrical duty, and it includes a plurality of individual conducting wires 14 having individual sheaths 16, an appropriate filler 18 and a cylindrical, resilient, protective, outer covering 20, which may be made of any suitable rubber or rubberlike material, natural or synthetic. As illustrated, the cable 10 comprises a three-wire cable; however, it will be understood that my improved cable rip may be employed with a cable having any desired number of wires.

The connector component 12 to which the cable It is connected comprises a cylindrical casing 22, which is preferably metallic, that has a radially inwardly extending flange 24 formed at one end having a central opening 26 formed therein. The details of construction of the interior of the connector component 12 and elernents which are located therein form no specific part of the invention being set forth in this patent application; however, for the sake of understanding the present invention, it should be understood that within the casing 22 there is disposed terminal means to which the bared ends of wires 14 are individually connected. In FIG. 6, the referred-to terminal means have been illustrated as individual clamp-type terminals 28 that are mounted in an appropriate insulating body 39, and it can there also be seen that the bared ends of wires 14 extend through appropriate openings in another insulating body 32 and are individually connected to individual terminals 23 It is the basic purpose of this invention to provide an improved grip in a connector component 12 for the cable .14), which Will relieve all strain that is imposed on the cable it) on the exterior of the connector component from the connections of the terminals 28 and ends of wires 14.

In order to efiect such a cable grip, the casing 22 has rigidly connected to its flange 24-, in any desirable manner, for example as by welding, a tubular portion in the form of a metallic, guiding-clamping member 34. Member 34 is generally cup-shaped and includes an annular, radially extending mounting flange 36 that is contiguous with casing flange 24, a cylindrical hub portion 38, and a radially inwardly directed, clamping flange 43 having a central opening 42 formed therein. In addition to the member 34-, the cable grip comprises a metallic clamping collar 44, a pair of spaced resilient, clamping bushings 46, and rigid spacing rings 48.

Clamping collar 44 is generally cylindrical and includes at one axial end a radially inwardly extending, clamping flange 50 that surrounds opening 52, and at the other axial end a radially outwardly extending annular wall 54 which terminates in an axially extending cylindrical flange 56. The dimensional relationship of the guidingclamping member 34 and clamping collar 44 is such that the clamping collar is slidably guided on the hub portion 38 of the member 34 and is arranged to have its cylindrical flange 56 concentrically disposed about the peripheral edge of the flange 36 of the member 3% when the parts are fully assembled, as illustrated in PEG. 6.

Each of the clamping bushings 46, one of which is illustrated by itself in FIG. 4, comprises a tubular memher having a plain cylindrical outer wall 58, a substantially plain cylindrical inner wall as and a pair of spaced, flat, parallel, end walls 62. A plurality of circumferentially spaced, axially extending grooves 64 are formed in the cylindrical inner wall 66 and extend completely axially therethrough. The clamping bushings 56 are resilient and may be made of any suitable rubberlike material, natural or synthetic. The clamping bushings are dimensioned to fit within the clamping collar 44.

Spacing rings 43 are rigid, preferably metallic, and are dimensioned so as to snugly but slida bly nestle within the clamping collar 44. Spacing rings 48 are disposed axially between clamping bushings 4 d to axially space the latter. The width, i.e. axial length, of the spacing rings 48 is such as to provide for desired predetermined de formation of the clamping bushings 45 when the cable grip parts are fully assembled, as will become apparent subsequently. In the illustrations, two separate spacing rings 48 are illustrated, each of a different width; however, as long as the aggregate axial length of the spacing ring or rings is that necessary to provide the de sired ultimate deformation of the clamping bushings, the particular number of spacing rings 48 employed is not important.

PEG. 3 illustrates the relative positions of the various parts of the connector component 12, particularly the parts of its cable grip, at the time when the cable 10 is about to be connected to the connector component 12, but prior to actual connection. In this condition, the parts of the cable grip are disposed so as to permit the cable 10 to be comfortably inserted through the cable grip so as to allow the individual wires of the cable to be connected to the terminal means within the connector component 12. It will be observed in FIG. 3 that the clamping bushings 46 and spacing rings 48 are disposed within the clamping collar between the clamping flanges 4:) and 5t}, with the central openings of all the cable grip parts aligned. At this stage in assem bly, the parts of the cable grip are poised to efiectuate firm radially inward clamping of the cable it on the occurrence of subsequent axial movement of the clamping collar 44- toward the connector component 12 from its FIG. 3 position to its PEG. 6 position, wherein it has been fully axially drawn toward the connector component 12 and is illustrated in its fully assembled condition. The means for physically attaching the clamping collar 44, and hence mounting all of the parts of the cable grip which it supports, to the connector component casing 22 and drawing it toward the connector component casing may conveniently comprise a plurality of machine screws 66. Four circumferentially spaced machine screws are illustrated (see FIG. 5), which individually pass through appropriate plain openings 68 in the annular wall 54' of clamping collar 44 (see FIG. 8) and are threadedly anchored in the flange 36 of the guiding-clamping member 34 and the flange 24 of casing 22, as by being threadedly received in nut members 79 which are rigidly mounted to the casing 22 in any known manner so as to be rigidly secured thereto.

It will, therefore, be apparent that when the parts are positioned as illustrated in FIG. 3, the clamping collar 44 is secured to the connector component casing 22 by the machine screws 66, but that it is spaced therefrom, as pointed out above. In this condition, a bared end of cable it) may be inserted through the opening 52 in the clamping collar clamping flange 50', the opening formed by the inner cylindrical wall 6%) of the adjacent clamping bushing 46, the central openings (unnumbered) in the spacing rings 48, the opening formed by the inner cylindrical wall as of the second clamping bushing 46, the opening 42 in the guiding-clamping member clamping flange 4i}, and then into the interior of the connector component casing 22.

After an end of the cable 10 has been inserted into the connector component, as illustrated in dotted lines in FIG. 3, the cable grip may be brought into operative effect by drawing clamping collar 44 axially toward the connector component casing 22 by tightening the machine screws 66. The eifect of such action is to reduce the axial distance between the face of the clamping collar clamping flange 59 that abuts one axial wall 62 of one of the clamping bushings 46 (the left-hand one in FIG. 3) and the face of the guiding-clamping member clamping flange 40 that abuts one axial wall 62 of the other clamping bushing 46 (the right-hand one in FIG. 3). The reduction of this axial distance, which originally is substantially the cumulative axial length of the clamping bushings and spacing rings, results in the axial compression and individual deformation of each of the clamping bushings 46.

In view of the fact that the clamping bushings 46 are restrained on all sides other than their radially inher sides, their inner cylindrical walls 60 arch or bulge radially inwardly, i.e. move radially inwardly, to the positions illustrated in FIGS. 6 and 7. The effect of such deformation is to substantially uniformly reduce the inner diameters of the cylindrical walls 69. A comparison of FIGS. 6 and 7 with FIGS. 3 and 5, respectively, will indicate the changes in the shape of the clamping bushings which are effected. In FIG. 3 it will be observed that the surfaces of the inner cylindrical walls 60 of the clamping bushings initially are straight when viewed in a radial plane, whereas they are definitely arched after final assembly, as viewed in FIG. 6. Also, the axial grooves 64 formed in the inner cylindrical walls 60 of the clamping bushings, which are shown in initial undistorted condition in FIG. 5, are substantially constricted on final assembly, as shown in FIG. 7. It will also be observed in FIG. 7 that the inner cylindrical wall 69, in addition to being of lesser diameter than it was in its free undistorted state, shown in dotted lines, remains substantially circular in radial cross section. This is desirable, as it enhances the gripping effect of the clamping bushings, and is permitted by the action of axial grooves 64 which, by constricting, allow for circumferential displacement of the material of the inner portions of the clamping bushings, on deformation of the latter, in addition to radial displacement, and thereby prevent localized circumferential bulging.

The cable grip on final assembly firmly grips the cable 10 circumferentially at two axially spaced portions. The elfect of the gripping action is to compress the resilient sheath 20 of the cable circumferentially at these two axially spaced portions and reduce the outer diameter of these portions of the sheath; this interengagement of the clamping bushings and sheath results in a highly effective cable grip. It should be realized that the axial spacing of the clamping bushings 46 eflected by spacing rings 48. which can be clearly seen in FIG. 6, provides for this desirable effect. The presence of the spacing rings 48 also prevents undesirable pinching action of the clamping bushings 46, which would occur on deformation of the latter in their absence. This pinching action involves the interengagement of contiguous portions of the radial faces of adjacent clamping bushings in a manner that produces non-uniform deformation of the clamping bushmgs.

In addition to providing for the cable to be gripped at two axially spaced portions, the cable grip also provides for highly effective, circumferential gripping at each of these two portions. This results from the substantially uniform reduction in the diameters of the cylindrical walls 60. Such substantially uniform diameter reduction, as pointed out above, is permitted by the axial grooves 64. It should be realized that in the absence of these channels, on compressing the clamping bushings axially, the latter would be deformed radially inwardly; however, they would not have their cylindrical walls 60 reduced uniformly in diameter. The radially inward deformation action of the cylindrical walls 60, in the absence of grooves 64, would produce a series of interconnected, axially extending ridges and valleys, because it would be necessary for the inner surfaces of the cylindrical walls 60 to wrinkle and fold over on themselves in order to deform radially inwardly. This action, which is referred to in the art as lumping, occurs because, in addition to radially inwardly deforming forces being generated on axial compression of the clamping bushings, there are also circumferential deforming forces generated at and near the inner surfaces of the cylindrical walls 60. Applicants clamping bushings are completely free from the undesirable lumping deforming action which would result in the absence of grooves 64, which would produce ineffective, non-uniform circumferential clamping of the cable ill. The presence of the grooves 64 permits clearance space to allow for circumferential deformation of the portions of the clamping bushings 46 adjacent the cylindrical walls 6%, resulting in the constriction of the grooves 64 after deformation of the clamping bushings, as can be clearly seen in FIG. 7. This circumferential deformation permits the inner surfaces of the cylindrical walls of to move inwardly without wrinkling and results in diffusing the deformation of the portions of the clamping bushings adjacent the cylindrical walls 60, which produces what is referred to in the art as a good mushy fit, and the consequent, desirable uniform reduction in the diameter of the latter.

The illustrated embodiment of my invention which has been described comprises a distinct improvement over all known cable grips generally, in that it is relatively simple in construction, easy to assemble and manipulate, and yet highly effective and superior as a cable grip. It has been found in practice that my cable grip provides a particularly effective means for clamping large, multi- Wire, electrical cables that are capable of heavy duty applications and which are extremely large in diameter, for example, in the order of three or more inches in diameter. When dealing with cables of this size, known electrical cord clamps, for example, of the vise-type employed with light duty, flexible, electrical cords, are not adequate or satisfactory. My improved cable grip securely clamps and provides a strain relief for very large electrical cables. Furthermore, notwithstanding the rather large, effective clamping forces which it generates, my improved cable grip is readily manipulated to permit insertion or removal of the cable from the connector component, simply by tightening or loosening the machine screws which connect the clamping collar to the casing of the connector component. Although my improved cable grip is particularly effective when used with very large cables, if desired, it could be, by an appropriate reduction in the size of its parts, used as a cord grip for smaller size electrical cords.

The illustrated embodiment of my invention constitutes the preferred form thereof. However, if desired, only a single clamping bushing may be employed with art appropriate reduction in the axial distance between the faces of the two clamping flanges. Also, as pointed out above, only a single spacing ring of appropriate axial length rather than two spacing rings may be employed if desired. Furthermore, if in practice it is found that it is desirable to generate greater clamping forces than are being generated at the time, it is simply necessary to substitute a spacing ring or rings of greater axial length than are being employed at the time. Further still, it should be realized that although the protective outer covering of the illustrated cable has been described as resilient, my cable grip may be employed with cables having outer coverings of other materials, including metals. However, my cable grip is most effective when utilized with a cable having a resilient outer cover. It has been found in practice that after substantial periods of use, of my cable grip on a resilient sheathed cable, on disassembly of the cable from my cable grip, definite and distinct, permanent, circumferential markings remain on the periphery of the cable at the two axially spaced portions where the clamping forces of the clamping bushings have been generated and applied to the cable.

As will be evident from the foregoing description, cer tain aspects of my invention are not limited to the particular details of construction of the example illustrated, and I contemplate that various and other modifications and applications will occur to those skilled in the art. It is, therefore, my intention that the appended claims shall cover such modifications and applications as do not depart from the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The combination of: an electrical cable and a connector component having a strain-relieving grip for the cable; said cable comprising an elongated cylindrical multi-wire cable having a resilient protective outer covering; said connector component comprising a casing internally supporting electrical terminal means and having a tubular portion on an end thereof with an inturned flat transverse end wall; an opening in said end wall to permit the insertion of an end of said cable into said casing so as to have its wires connected to said terminal means; a cup-shaped clamping collar detachably secured to said casing at said end and arranged to house a pair of similar spaced clamping bushings; each of said bushings being tubular, resilient and having a continuous cylindrical outer wall and a plurality of circumferentially spaced axially extending grooves formed in its inner cylindrical wall and extending axially completely therethrough; said bushings arranged to be disposed within said collar adjacent said end wall on the exterior of said casing about said cable when it extends into said casing, and the defined element being dimensioned so as to deform said clamping bushings when said clamping collar is secured to said casing in final assembled position so as to uniformly reduce the inner diameters of the inner cylindrical walls of said clamping bushings and cause them to firmly circumferentially grip said cable at two axially spaced circumferential portions.

2. The combination defined in claim 1 wherein said tubular portion comprises a cup-shaped guiding-clamping member that is rigidly secured to said casing; and said clamping collar is operationally associated with it to both effect mounting of said clamping collar on said casing and deformation of said clamping bushings.

3. The combination defined in claim 1 wherein said clamping bushings are spaced by rigid ring-like spacing means.

4. The combination defined in claim 1 wherein said casing end wall comprises a cup-shaped guiding-clamping member that is rigidly secured to said casing; said guidingclamping member includes a hub portion for supporting said clamping collar and a radial flange that is disposed within said clamping collar when the latter is mounted on said hub portion; and said clamping collar includes a radial flange spaced from the radial flange of said member; said clamping bushings are spaced by rigid ringlike spacing means; and said clamping bushings and said spacing means are disposed within said clamping collar between said radial flanges, whereby the latter function as means which deform said clamping bushings when the parts are fully assembled.

5. The connector defined in claim 1 wherein said clamping collar is secured to said casing by a plurality of circumfereutially spaced axially extending screws that are 5 individually threadedly secured to said casing.

References Cited in the file of this patent UNITED STATES PATENTS Abbott Oct. 24, 1939 Richardson et a1 Nov. 30, 1948 Hargett July 29, 1952 Young Jan. 4, 1955 Humphrey Feb. 21, 1956 Agron et a1. June 19, 1962 FOREIGN PATENTS France July 27, 1931 OTHER REFERENCES German printed application St 6281, Oct. 18, 1956.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N00 3 I21 6OO February 18 1964 Joseph Fe Healy It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6, lines 47 and 48 for "element" read elements n,

Signed and sealed this 7th day of July 1964.

(SEAL) Attest:

EDWARD J BRENNER Commissioner of Patents ERNEST W. SWIDER Attesting Officer 

1. THE COMBINATION OF: AN ELECTRICAL CABLE AND A CONNECTOR COMPONENT HAVING A STRAIN-RELIEVING GRIP FOR THE CABLE; SAID CABLE COMPRISING AN ELONGATED CYLINDRICAL MULTI-WIRE CABLE HAVING A RESILIENT PROTECTIVE OUTER COVERING; SAID CONNECTOR COMPONENT COMPRISING A CASING INTERNALLY SUPPORTING ELECTRICAL TERMINAL MEANS AND HAVING A TUBULAR PORTION ON AN END THEREOF WITH AN INTURNED FLAT TRANSVERSE END WALL; AN OPENING IN SAID END WALL TO PERMIT THE INSERTION OF AN END OF SAID CABLE INTO SAID CASING SO AS TO HAVE ITS WIRES CONNECTED TO SAID TERMINAL MEANS; A CUP-SHAPED CLAMPING COLLAR DETACHABLY SECURED TO SAID CASING AT SAID END AND ARRANGED TO HOUSE A PAIR OF SIMILAR SPACED CLAMPING BUSHINGS; EACH OF SAID BUSHINGS BEING TUBULAR, RESILIENT AND HAVING A CONTINUOUS CYLINDRICAL OUTER WALL AND A PLURALITY OF CIRCUMFERENTIALLY SPACED AXIALLY EXTENDING GROOVES FORMED IN ITS INNER CYLINDRICAL WALL AND EXTENDING AXIALLY COMPLETELY THERETHROUGH; SAID BUSHINGS ARRANGED TO BE DISPOSED WITHIN SAID COLLAR ADJACENT SAID END WALL ON THE EXTERIOR OF SAID CASING ABOUT SAID CABLE WHEN IT EXTENDS INTO SAID CASING, AND THE DEFINED ELEMENT BEING DIMENSIONED SO AS TO DEFORM SAID CLAMPING BUSHINGS WHEN SAID CLAMPING COLLAR IS SECURED TO SAID CASING IN FINAL ASSEMBLED POSITION SO AS TO UNIFORMLY REDUCE THE INNER DIAMETERS OF THE INNER CYLINDRICAL WALLS OF SAID CLAMPING BUSHINGS AND CAUSE THEM TO FIRMLY CIRCUMFERENTIALLY GRIP SAID CABLE AT TWO AXIALLY SPACED CIRCUMENTIAL PORTIONS. 